1. Technical Field
The present invention relates to a conveyor for sheet-shaped thin plates, which are especially butted against and welded each other, and a method of conveying the same.
2. Related Art
For example, in a case where steel plates having different materials and thicknesses are used for forming adjacent portions or parts of, for example, a vehicle body, it is necessary to weld two or more sheet-shaped thin plates (steel plates), which are previously cut into fine rectangle shape, continuously in a longitudinal direction by using a continuous welding apparatus, thus forming tailored blank material.
As a method of welding the sheet-shaped thin plates to form the tailored blank material, there is provided a method in which a plurality of sheet-shaped thin plates are fixed in a state in which end surfaces thereof are butted against each other with no gap therebetween, a plurality of sheet-shaped thin plates are welded by using a welding machine movable along the joined portion. There is also provided a method in which a plurality of sheet-shaped thin plates are moved in a state in which end surfaces thereof are butted against each other and then welded to each other by using a fixed type welding machine.
The continuous welding apparatus utilizing the above method for moving the sheet-shaped thin plates includes conveying members respectively for each of two thin plates, and each of the conveying members has a conveying surface inclined at an acute angle and having a step in the vertical direction. These conveying surfaces merge into a common horizontal surface at a portion just before the welding machine, for example, as disclosed in Japanese Patent Publication No. HEI 6-13153.
According to the conveying member of the sheet-shaped thin plate used for the continuous welding apparatus disclosed in this Patent Publication, however, the conveying surfaces are inclined at an acute angle and have the steps in the vertical direction, and the conveying surfaces merge into the common horizontal surface just before the welding members, i.e., welding position. Therefore, if the adjustment of guide members provided for the respective conveying members is not made precisely, there may cause an adverse possibility such that the ends to be welded of the thin plates are superposed in the vertical direction, or a gap is created therebetween. Hence, the good welding condition cannot be expected, thus being inconvenient.
Moreover, since the conveying members are themselves provided for the respective two thin plates, the adjustment therebetween, for example, in positional adjustment, requires much time and labor, including extra working.
Furthermore, the guide surfaces of the guide members are always slidably contacted to the ends to be welded of the thin plates, and hence, the change of the guide positions due to wearing may be envisioned. However, in a structure in which two thin plates are guided from opposing sides by different conveying surfaces, the relative position of the guide surfaces (surfaces to be guided) may be changed by the wearing, and in progressing of such wearing, the ends to be welded may be superposed vertically. Thus, periodical inspection for the relative positional adjustment between two thin plates will be required, thus being inconvenient.
Then, there is proposed guide rollers, as guide members, for determining a conveying center of the sheet-shaped thin plates. An end surface of the thinner thin plate (thin plate, hereinafter) is butted against an end surface of the thicker thin plate (thick plate, hereinafter) by the guide rollers so that the butted surfaces are located at constant positions. There is also proposed a technique in which the thin plate is deformed into corrugated shape to be slidable with an end surface of the thick plate.
At that time, if the guide roller is directed horizontally (its rotation axis is directed in the vertical direction), since the thick plate takes ideal rolling contact, the degree of wearing may be reduced. However, since the thin plate must bypass the guide rollers, the deformation amount thereof will be inevitably increased, straightness of a butted surface is made worse, and adhering condition with respect to the thick plate is deteriorated.
In addition, it is necessary to separately provide an additional member for deforming the thin plate into a corrugated shape, and thus, the entire structure of the apparatus will become complicated.
In this regard, if the guide roller is directed vertically (its rotation axis is directed in the horizontal direction), the thin plate which passes below the guide roller will take an ideal corrugated shape, but the width of the guide roller has to be widened in accordance with the moving amount toward the central portion of the sheet-shaped thin plate. As a result, resistance is generated when the thin plate is deformed into the corrugated shape and this adversely affects the conveying operation, which may cause a fear such that the conveying speed becomes unstable.
In addition, there is a further adverse possibility that a contact area between the guide surface of the guide roller and the thick plate is increased, the conveying resistance is increased due to the slide contact therebetween, and the wearing is hence increased. Furthermore, it is necessary to chamfer the guide surface of the guide roller to prevent the biting between the guide surface of the guide roller and the thick plate, which may result in that the deformation amount of the thin plate is increased by the chamfered amount, the straightness of the butted surface is made worse, and the adhesion to the thick plate is deteriorated.